Generally, a vehicle includes a starter motor which drives an engine and an alternator which generates power using rotating force of the engine.
The starter motor rotates an engine when battery power is supplied.
The alternator generates alternating current power when a rotor rotates by driving force of the engine while a magnetic field is formed and charges a battery with the alternating current power using a rectifier or the like.
Both of the starter motor and the alternator have a very similar structure by having a stator and rotor structure, and may be operated as a generator or a motor depending on whether force or power is applied.
Recently, a belt driven starter and generator (BSG) motor which can function as a starter motor and an alternator with a single structure has been actively studied.
The motor generates heat in a process of rotation, and thus it is important to quickly discharge the generated heat to the outside to prevent the performance of the motor from being degraded. Particularly, it is more important when a motor, such as the BSG motor which simultaneously performs starter motor and alternator functions, has a structure of high-speed rotation.
Also, a motor noise is also an important factor to determine the performance of the motor, and thus it is important to minimize the noise.